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What Causes a Car to Shake?

You’re driving down the interstate, and as you come up to cruising speed, the steering wheel starts to vibrate in your hands. You grip a little tighter and press the accelerator a little more. The vibration gets worse, and it feels like your molars are going to vibrate right out of your mouth. But traffic is still passing you at breakneck speed, so you speed up a little more. The vibration seems to dissipate and you relax into your commute.

What causes your car to shake? Sometimes it’s just a little annoyance that goes away on its own, and other times it progresses so quickly you feel like you’re sitting on a washing machine in the agitate cycle. Many things can cause your vehicle to vibrate or shake. Here are a handful of causes to watch out for.

Tire balancing

The simplest and most common reason for your vehicle to shake is tire balancing. Balancing a tire is a process of adding small amounts of weights to each wheel or rim with a tire installed on it. They are placed strategically with the assistance of a machine that spins the assembly when it is removed from your car with the purpose of making the wheel’s weight perfectly balanced all the way around.

A simple half ounce of weight can cause a noticeable vibration when driving. It can also cause premature or abnormal tire wear. Wheel balancing problems can be felt at highway speeds predominantly, especially 55-65 miles per hour. Sometimes the vibration is unnoticeable at speeds higher than 65 mph.

Tires are balanced when they are installed, or at least they should be. Sometimes a weight can fall off. Tire balancing should be corrected to prevent unnecessary costs associated with premature tire wear.

Bent rim

Have you ever gone up on a curb when parallel parking? Have you ever hit a pothole really hard that you couldn’t avoid in time? A sudden impact on your wheel can cause a bent rim.

A bent rim exhibits a similar symptom as tire balance issues. In most cases, the only difference is when the vibration is noticeable. When a rim is bent bad enough for a vibration to occur, it’s felt at 40 miles per hour and faster. This kind of vibration doesn’t go away when driving at higher speeds.

A bent rim needs to be addressed for safety reasons. The tire’s seal on the rim can be compromised and a blowout or sudden loss of tire pressure is possible. The tire can also wear unevenly like a tire balance issue. Often, a rim can be straightened or repaired instead of replaced, depending on the severity.

Tire separation

Tire separation doesn’t mean the tire came off. It means that the layers of rubber in the tire that have been laminated together are coming apart. You may notice a bulge in the sidewall of the tire, or a goose egg on the tread on close examination, but it may not be visible to the naked eye either.

The most common cause of tire separation is contact with a curb or pothole. The layers of the tire get pinched, and air inside the tire gets between them. Essentially, the tire isn’t totally round anymore and causes a vibration. The separation can be a safety concern as the tire is significantly weaker at that spot. A lumpy driving feeling at low speeds progresses to a fast vibration at higher speeds when a tire separation occurs.

Unfortunately, the only correction for tire separation is to replace the affected tire. This may mean replacing two or four tires to ensure the tread wear is the same on all your tires.

Steering components loose

If you’re vehicle has a few years on it, or is higher mileage, you may notice the steering isn’t quite as responsive as it used to be when you first purchased your car. That’s quite common; steering components wear. There may be a little more play in the steering wheel before your car reacts to your input. That’s caused by steering component wear.

Tie rod ends are the links from your steering gear, or rack and pinion, to the wheels. They are a small ball and socket that allows for travel vertically and horizontally. When these tie rod ends become loose, the wheel isn’t kept solidly pointing the direction you are steering it. There is side to side movement allowed, and a tie rod that is excessively loose can cause a bad vibration at any speed, and it will likely happen on and off randomly. The same can be said for the inner tie rods, or any other steering component that has wear.

When a vibration occurs from a steering component, only a trained professional will be able to determine and repair it. Have a vibration checked expediently.

Loose wheel bearing

A loose wheel bearing will cause much the same symptom and in similar circumstances to a loose steering component, and that is because they are closely related. The wheel bearing allows the wheel to rotate freely while maintaining a solid mount to the vehicle. If the wheel bearing wears out or gets loose, the wheel has play to move around when driving at any speed. The shake that occurs can come and go, and doesn’t follow any sort of regular pattern.

A wheel bearing sometimes be repacked and adjusted on a few certain styles of vehicle, however by far the most common style of wheel bearing is one mounted in the wheel hub. If this wheel hub has play, it is replaced as an assembly, and can’t be serviced otherwise.

Brake pulsation

Your brakes can also cause your vehicle to shake, and is the most common cause of your vibration if it only shows up when you are decelerating. Brake pulsation is caused the the brake rotors or drums on your vehicle are no longer perfectly flat. When the brake pads press against the rotor, it isn’t able to apply constant continuous pressure. It causes a sudden and high frequency vibration in the vehicle that diminishes as you come to a stop.
Brake pulsation needs to be addressed as soon as possible due to its effect on safety. Brake pulsation increases your stopping distance and can cause loss of control in slippery conditions.

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